The Sherman Firefly was a World War II British variant of the American Sherman tank, fitted with the powerful British 17-pounderanti-tank gun as its main weapon. Originally conceived as a stopgap until future British tank designs came into service, the Sherman Firefly became the most common vehicle with the 17-pounder in World War II.

Firefly IC Hybrid - Germany, 1945

After the problem of getting the gun to fit in the Sherman's turret was solved, the Firefly was put into production in early 1944, in time to equip Field Marshal Montgomery's forces for the Normandy landings. It soon became highly valued as the only British tank capable of defeating the Panther and Tiger tanks it faced in Normandy at standard combat ranges. In recognition of this, German tank and anti-tank gun crews were instructed to attack Fireflies first. Between 2,100 and 2,200 were manufactured before production wound down in 1945.

Origins:

The concept of fitting a 17-pounder gun into a Sherman tank had initially been rejected by the Ministry of Supply's Tank Decision Board. Although the British Army had made extensive use of the American-built Sherman tank, it was intended that a new generation of British tanks would replace it in the anti-tank role. First there was the Cromwell tank, which was expected to use the Vickers High Velocity 75 mm gun; this gun would have had superior anti-tank performance to the US 75 mm and 76mm guns that were mounted in the Sherman. The second was the A30 Challenger which was based on the Cromwell but with the even more powerful 17-pounder gun. These two tanks - and their successors, the Comet and the Centurion, which were already on the drawing board - were to have replaced the Sherman in British service, and so the prospect of spending time and money mounting a 17-pounder on the Sherman was not seen as desirable.

17 pdr anti-tank gun in action

Nonetheless several unofficial attempts were made to upgun the Sherman. The earliest attempt can be credited to Major George Brighty of the Royal Tank Regiment while he was at Lulworth Armoured Fighting School in early 1943. Despite the fact the A30 Challenger was undergoing initial trials at Lulworth, Brighty was convinced that the Sherman was a better mount for the 17-pounder. However he was stymied by the turret of the Sherman, which was too small to allow for the very long recoil of the gun. In a rather desperate move, Brighty removed the recoil system and locked the gun in place, thus forcing the entire tank to absorb the recoil, but this was a far from ideal situation and there was no telling how long the tank would have been able to handle such a set-up.

Firefly VC with crest of Lulworth Gunnery School

Around June 1943, a colleague of Brighty, Lt. Col. George Witheridge of the Royal Tank Regiment, arrived at Lulworth. A veteran of the North Africa campaign, Witheridge had experienced firsthand the lopsided battles between British tanks armed with 2-pounder guns against Rommel's formidable panzers and anti-tank guns. During the disastrous Battle of Gazala in mid 1942, Witheridge had been blown out of his Grant tank, and though he recovered from his wounds, he was declared unfit to return to combat duty. Instead, in January 1943, he was posted to Fort Knox in the United States for six months to advise on gunnery, where he was "sold" on American tanks. While at Lulworth, Witheridge inspected the A30 Challenger, and "joined in the chorus of complaints" about the tank. Upon looking up Brighty and learning of his attempts to use the Sherman, Witheridge lent his assistance. He advised Brighty on methods to solve the recoil issue.

Not long after, Witheridge and Brighty received a notice from the Department of Tank Design (DTD) to cease their efforts. Unwilling to abandon the project, Witheridge, using his connections with such influential people as Major General Raymond Briggs, former GOC of the 1st Armoured Division in North Africa and now Director of the Royal Armoured Corps, and successfully lobbied Claude Gibb, Director General of Weapon and Instrument Production at the Ministry of Supply, to make it an official ministry project. In doing so, the endeavour was taken out of the hands of the highly enthusiastic and devoted amateurs at Lulworth who had initiated it and given to professional tank developers.

Design:

It was W.G.K. Kilbourn, a Vickers engineer at the time working for the Department of Tank Design, who transformed the prototype into the tank that would serve the British forces from D-day onwards. The first thing Kilbourn had to fix was the lack of a workable recoil system for the 17-pounder. The 17-pounder travelled 1.0 m back as it absorbed the recoil of the blast. This was too long for the Sherman turret. Kilbourn solved this problem by redesigning the recoil system completely rather than modifying it. The recoil cylinders were shortened to allow the turret to take the gun and its recoil, and the new cylinders were placed on both sides of the gun to take advantage of the width of the Sherman's turret rather than be hindered by its height.

The gun breech itself was also rotated 90 degrees left to allow for loading from the left rather than from on top.

Notice the different positions of 17 pdr gun breech
between a normal 17 pdr. and the tank gun

The radio which was mounted in the back of the turret in British tanks had to be moved. An armoured box (a "bustle") was attached to the back of the turret to house the radio. Access was through a large hole cut through the back of the turret.

Firefly turret - rear bustle

The next problem encountered by Kilbourn was that the gun cradle, the metal block the gun sits on, had to be shortened to allow the gun to fit into the Firefly, and thus the gun itself was not very stable. Kilbourn had a new barrel designed for the 17-pounder that had a longer untapered section at the base, which helped solve the stability problem. A new mantlet was designed to house the new gun and accept the modified cradle. The modifications were extensive enough to require that 17-pounders intended for the Firefly had to be factory built specifically for it.

Kilbourn had to deal with other problems. On the standard Sherman tank, there was a single hatch in the turret through which the tank commander, gunner and loader entered and left the tank. However the 17-pounder's larger breech and recoil system significantly reduced the ability of the loader to quickly exit from the tank if it was hit. As a result, a new hatch was cut into the top of the turret over the gunner's position.

The final major change was the elimination of the hull gunner in favour of space for more 17-pounder ammunition, which was significantly longer than the 75 mm shell and thus took up more room. The MG position was closed by an armoured plug.

The .30 position closed by an armoured plug (arrow)

The Firefly had no armour or mobility advantages over the normal Sherman tank, although the gun mantlet was some 13mm thicker.

By October and November 1943, enthusiasm began to grow for the project. The 21st Army Group was informed of the new tank in October 1943. Even before final testing had taken place in February 1944, an order for 2,100 Sherman tanks armed with 17-pounder guns was placed. This reaction was understandable, as the Challenger program was suffering constant delays and few would be ready for Normandy, and even worse, the realization that the Cromwell tank did not have a turret ring big enough to take the new High Velocity 75 mm gun (50 calibres long), so the Cromwell would have to be armed with the general purpose Ordnance QF 75 mm. Thus the Sherman Firefly represented the only available tank with firepower superior to the QF 75 mm gun in the British Army’s arsenal. Not surprisingly, it was given the ‘highest priority’ by Winston Churchill himself.

Let's hear the Man !!!

The nickname "Firefly" is not found in wartime official documents. It was sometimes used at unit level (Brigade/Regiment) war diaries from March 1944, with another nickname being 'Mayfly'. During the war, Shermans with 17-pounder guns were usually known as '1C', '1C Hybrid', or 'VC', depending on the basic mark of the vehicle. In British nomenclature, a "C" at the end of the Roman numeral indicated a tank equipped with the 17-pounder.

Armament:

The main armament of the Sherman Firefly was the Ordnance Quick-Firing 17-pounder. Designed as the successor to the British QF 6-pounder, the 17-pounder was the most powerful British tank gun of the war, and one of the most powerful of any nationality, being able to penetrate more armour than the 8.8 cm KwK 36 fitted to the German Tiger I, or the Panther tank's 7.5 cm KwK 42. The Firefly 17-pounder was able to penetrate some 140 mm of armour at 500 m and 131 mm at 1,000 m using standard Armour Piercing, Capped, Ballistic Capped (APCBC) ammunition at a 30-degree angle. Armour Piercing, Discarding Sabot (APDS) ammunition could penetrate some 209 mm of armour at 500 m and 192 mm at 1,000 m at a 30-degree angle, which on paper could defeat the armour of almost every German armoured fighting vehicle at any likely range. However, early production APDS rounds lacked accuracy, and the 50 mm penetrator was less destructive after it had penetrated enemy tank armour than the 76.2 mm APCBC shell. In any case, APDS ammunition was rare until late 1944.

Despite the Firefly's superior antitank capabilities, the tank was regarded as inferior to the regular Sherman against soft targets such as enemy infantry, buildings and lightly armoured vehicles. As the war in Europe neared its close, the Allies found themselves encountering these more often than heavy German tanks. Allied tank units therefore typically refused to completely switch to Fireflies. A good HE shell only became available in late 1944 and even then was not as potent as the standard Sherman 75 mm HE shell. Another problem was that the powerful blast from the 17-pounder gun kicked up large amounts of dirt as well as smoke, making it difficult for the gunner to observe the fall of the shell, forcing him to rely on the commander to observe it and to order corrections. Dirt and dust revealed the position of the tank, so Sherman Fireflies would have to move every few shots. The recoil and muzzle blast could be severely jarring to Firefly crews and the muzzle blast frequently caused night blindness as well.

17 pdr. firing. Notice the recoil and the dust cloud...

This was a common problem on any tank armed with a high velocity gun, including Panther and Tiger tanks. The cramped nature of the turret meant that loading the large 17-pounder shell was difficult, so Fireflies had a lower rate of fire compared to regular M4 Shermans. Since the Firefly was a stopgap, these problems were never eliminated, as the Firefly was to be retired with the introduction of the new British tank designs.

The Firefly's secondary armament was the standard .30 inch coaxial machine gun in the turret. The hull mounted machine gun had been removed to increase ammunition storage for the main gun. A top-mounted .50 calibre machine gun was also attached, though many crews removed it due to its awkward mounting and position near the commander, which limited a full 360 degree view when unbuttoned in battle.

The rockets, accurate when fired from aircraft, were less accurate when fired from a tank as they were being fired from a stationary point and had little slipstream over the fins. Despite this, the RP-3 was effective when its 27 Kg warhead hit the target.

60 lbs rockets in Sherman turret= Sherman Tulip

These were used at the Rhine Crossing by the tanks of a single squadron of the 1st Coldstream Guards. These tanks, called "Sherman Tulips", were conventional Shermans and Fireflies.

Another close-up of the 60 lbs. rockets in Sherman turret

Tulips (Firefly IC and Sherman 75mm) from 1st Coldstream Guards

Production:

Three different variants of Sherman Firefly served during the Second World War, each based on different variants of the M4 Sherman. The Firefly conversion was carried out on Sherman I (M4), Sherman I Hybrid (M4 Composite) and Sherman V (M4A4) tanks.

Sherman Firefly IC (M4)
Based on a George Bradford drawing

Sherman Firefly IC Hybrid Hull (M4 Composite)
Based on a George Bradford drawing

Sherman Firefly VC (M4A4)
George Bradford drawing

Some sources state that several Sherman IIs (M4A1) were converted and used in action, but photos allegedly showing these conversions are in fact views of the front half of Sherman I Hybrid Fireflies. To complicate matters, a very small number of Canadian licence-built Sherman IIs (M4A1), the Grizzly, were converted to Fireflies in Canada and used for training, but none saw action. The majority of Shermans converted were the Sherman V/M4A4 model, of which the British received about 7,200.

A Sherman VC Firefly in Bocage, France - 1944.

The Sherman VC and IC variants are easily distinguished by their lower hulls; the VC having a riveted lower hull with a curved shape while the IC has a welded and angled lower hull. The Hybrid can be distinguished by its upper hull which is cast and which gives it a distinctive curved look in comparison to the more boxy hull of a typical Sherman.

Sherma Firefly IC
Notice the duckbills and the spare tracks (Churchill) as armour

Production of the Firefly started in early 1944, and by May 31, some 342 Sherman Fireflies had been delivered to Montgomery's 21st Army Group for the D-Day landings. As a result, British tank troops were composed of three regular Shermans and one Firefly. The same distribution occurred in Cromwell units, but this caused logistical problems, as each Cromwell troop now needed to be supplied with parts for two different tanks, and the Fireflies were slowly replaced by Challenger tanks as they came out. Churchill units received no Fireflies, and as a result often had to rely on any attached M10 or M10 Achilles units to provide increased firepower to deal with tanks their 75 mm guns could not eliminate.

Polish Fireflys: The first is IC and the others, IC Hybrids

Production was limited by the availability of suitable tanks, with the phasing out of 75 mm Sherman production. To make up numbers the Mark I "hybrids" were employed. From D-Day in June to the end of the Battle of Normandy in late August, some 550 Sherman Fireflies were built, more than sufficient to replace any permanent tank losses during the battle. In late 1944, with the creation of an effective high-explosive shell for the 17-pounder gun, British units started to receive two Fireflies per troop. By February 1945, some 2,000 Sherman Fireflies had been built and British armour troops were equipped with a 50/50 mix of 75 mm and 17-pounder-armed Shermans.

In the spring of 1945, production of the Firefly was scaled down, with the last tank being delivered in May 1945. This was the result of several factors, from superior home-grown designs like the Comet and Centurion coming into service which would replace the Firefly, to the impending defeat of Nazi Germany, and the inferior design of Japan's tanks, which it seemed would be the next opponents the British would have to face after the fall of Germany.

Overall production of the Sherman Firefly reached some 2,100 - 2,200 tanks; exact numbers are hard to determine as documents give contradictory totals. Jane's World War II Tanks and Fighting Vehicles gives a production of 1783 over 1944 and 563 over 1945, for a total of 2346.

Service:

Normandy

Fireflies were introduced to armoured brigades and divisions in the 21st Army Group in 1944 just in time for the Normandy landings. The timing was fortunate as the Allies discovered that the Germans were fielding a much larger number of formidable tanks, such as the Panther, than had been expected in the Normandy theatre. In fact the Allies had mistakenly assumed the Panther, like the Tiger, would be a rare heavy tank with a limited production run, rather than a total replacement for their medium tanks, and the larger-than-expected number of Panthers came as a nasty shock to the Allied commanders as well as the tank crews forced to engage them with guns that could not penetrate the frontal armour at anything other than short range.

Ken Tout, who served as a tank gunner and tank commander in the 1st Northamptonshire Yeomanry in Normandy in 1944, described the effect of mounting a 17-pounder in the Sherman:

The Firefly tank is an ordinary Sherman but, in order to accommodate the immense breech of the 17-pounder and to store its massive shells, the co-driver has been eliminated and his little den has been used as storage space. ... The flash is so brilliant that both gunner and commander need to blink at the moment of firing. Otherwise they will be blinded for so long that they will not see the shot hit the target. The muzzle flash spurts out so much flame that, after a shot or two, the hedge or undergrowth in front of the tank is likely to start burning. When moving, the gun's overlap in front or, if traversed, to the side is so long that driver, gunner and commander have to be constantly alert to avoid wrapping the barrel around some apparently distant tree, defenceless lamp-post or inoffensive house.

A Firefly IC Hybrid

Urban fight: a very dangerous place for a tank. Firefly IC Hybrid

Fireflies were deployed as one tank per troop of Cromwell or Sherman tanks. The deployment with Cromwell troops made servicing and supply of those units more complex. The Firefly was also slower than the Cromwell.

Panthers and Tigers accounted for only 30% of the 2,300 German tanks deployed in Normandy; the rest being Panzer IVs, Sturmgeschütz IIIs and other tanks that the 75 mm gun Shermans were able to effectively handle. However, the importance of Caen and Montgomery's operations, which pinned German armoured forces in front of the British positions so the American units could break out to the west, meant that British and Commonwealth units had to face over 70% of all German armour deployed during the Battle of Normandy, as well as over half of the elite, well-equipped Waffen-SS Panzer units. As a result, the Sherman Firefly was perhaps the most valued tank by British and Commonwealth commanders, as it was the only tank in the British Army able to effectively defeat the Panthers and Tigers at the standard combat ranges in Normandy.

This fact did not go unnoticed by the Germans, who realized that these long-barrel Shermans posed a much greater threat to their heavy tanks than the regular Shermans, and German tank crews and anti-tank gun crews were instructed to eliminate Fireflies first. Similarly, the Firefly crews realized that the distinctive long barrel of their 17-pounder gun made the Firefly stand out from regular Shermans, so crews attempted to disguise their tanks in the hope they would not be targeted. Some crews had the front half of the gun barrel painted white on the bottom and dark green or the original olive drab on the top to give the illusion of a shorter gun barrel.

Polish tankers in oath. Notice the cammo in the 17 pdr. gun barrel

Another suggestion was for a shorter wooden dummy gun to be mounted on the rear of the turret and point forward; however, this tactic does not appear to have been used in combat.
Despite being a high priority target, Fireflies appear to have had a statistically lower chance of being knocked out than standard Shermans; this was probably due more to how they were employed than to the actual effectiveness of the attempted camouflaging of the long barrel. Given the high value placed on Fireflies, a common tactic was for commanders to reconnoitre the battlefield before a battle to look for good hull down positions. During the battle, Firefly tanks would stay behind in those positions and cover the regular Shermans as they pushed forward, eliminating any enemy tanks that revealed themselves when they opened fire on the advancing Shermans and only moving forward when the regular Shermans had secured the area, or when they could no longer cover them from their current position.
Similarly, when on the move, troop commanders tended to position Fireflies in the rear to reduce the chance of them being knocked out. However, given the relatively unpredictable nature of battle, this setup was not always practical or possible, and many times, Fireflies were forced to engage enemies in the open where they could be identified.

Despite this, the Firefly's increased firepower was much valued, and during many engagements, the Firefly proved its worth, knocking out Tigers and Panthers at long range, as well as less formidable tanks like the Mark IVs and StuGs.

One example of this increased firepower was displayed by Lt. G. K. Henry's Firefly during the defense of Norrey-en-Bessin on 9 June against an attack by the 3rd Company of the 12th SS Panzer Regiment of the 12th SS Panzer Division. Determined to capture the town in preparation for a larger offensive to drive the British and Canadians back into the sea, Kurt Meyer ordered an attack by 12 Panthers of the 3rd Company and infantry to attack Norrey and drive the Canadians out of the town. The attack got under way at 1300 hours with the Panthers racing to the town at full speed only to stop to fire their guns, quickly outrunning their infantry support which was forced to the ground by Allied artillery fire. Within 1,000 m of the town, nine Shermans of the 1st Hussars opened fire into the advancing Panthers' flanks. Lt. Henry's gunner, Trooper A. Chapman, waited until the Panthers "lined up like ducks in a row" and quickly knocked out five with just six rounds. The attack was repulsed with the loss of seven of the 12 Panthers.

A similar example occurred on 14 June, during Operation Perch. Sgt. Harris of the 4th/7th Dragoon Guards, along with three standard Shermans, set up defensive positions along with the infantry after successfully driving out the Germans in the village of Lingèvres, near Tilly-sur-Seulles. Looking through his binoculars, Sgt. Harris spotted two Panthers advancing from the east. He opened fire at a range of 800 metres, knocking out the lead Panther with his first shot, and the second Panther with his second. Relocating to a new position on the other side of the town, he spotted another three Panthers approaching from the west. From his well-concealed flanking position, he and his gunner, Trooper Mackillop, eliminated all three with just three rounds. Harris and his gunner had knocked out five Panthers with as many rounds, demonstrating the potency of the Firefly, especially when firing from a defensive position on advancing enemy tanks.

While B Squadron stayed around the village, A and C Squadrons moved further south into a wood called Delle de la Roque. C Squadron positioned themselves on the east side of the woods and the understrength A Squadron in the southern portion with No. 3 Troop on the western edge of the wood From this position, they overlooked a large open section of ground and were able to watch as German tanks advanced up Route nationale 158 from the town of Cintheaux. Under strict orders from the troop commander, they held their fire until the German tanks were well within range. Ekins, the gunner of Sergeant Gordon's Sherman Firefly (Velikye Luki - A Squadrons tanks were named after towns in the Soviet Union) had yet to fire his gun in action. With the Tiger tanks in range, the order was given to fire. What followed was an almost 12 minute battle that saw Ekins destroying all three Tigers that No. 3 Troop could see; there were actually seven Tiger tanks in the area heading north along with some other tanks and self-propelled guns. A short time later, the main German counterattack was made in the direction of C Squadron. A Squadron (less Sgt Gordon who had been wounded and had already bailed out of the Firefly) moved over to support them and in the resulting combat, Ekins destroyed a Panzer IV before his tank was hit and the crew were forced to bail out. One of the Tigers Ekins is credited with knocking out was that of Michael Wittmann, though there is still some controversy over whether Ekins really killed Wittman, as Sherman Fireflies of the Sherbrooke Fusilier Regiment also fired at the Tigers from a closer range of 150 m.

Italy:

Overall the Firefly proved itself to be very successful, despite being intended as a stopgap until future British tanks like the Comet and the Centurion came into service. Although the Normandy campaign had priority, Fireflies also served with distinction in Italy in British and Commonwealth units. British units in Italy also used the Sherman with the US 76mm gun.